The purpose of this study is to characterize cardiopulmonary and aortocarotid baroreceptor activity, sympathetic efferent neuroeffector junction function and abnormalities of endothelium-dependent and independent relaxing or constricting factor release in four groups of patients: 1) hypertensive post-cardiac transplant patients treated with cyclosporine; 2) hypertensive post renal or bone marrow transplant patients receiving cyclosporine, 3) essential hypertensives not receiving cyclosporine and with no evidence of CHF.